Hot on One Side, Cold on the Other?
When your AC refuses to blow or your heater is stuck on full blast, the problem is often the brain of the system: the Climate Control Module (HVAC).
Note: While Highway 71 Auto Parts specializes in Engine and Transmission Control Modules (ECM/TCM), we provide these diagnostic guides as a free resource to help you troubleshoot other common automotive electronics. Please note that we do not currently stock replacement units for the module described in this specific guide.
Brain vs. Brawn: What’s Failing?
Modern climate systems (especially dual-zone “Auto” systems) use a dedicated module to command blend door actuators. These are small electric motors that move flaps inside your dash.
👨🔧 Tech Note: The “Clicking” Dash
“If you hear a repetitive clicking noise behind your glovebox when you change the temperature, your module is likely fine, but your **blend door actuator** has stripped its plastic gears. Don’t replace the module yet!”
Symptoms of a Faulty HVAC Module
- ✅ No Blower Function: The screen works, but the fan never turns on (Check the Resistor first!).
- ✅ Dark Display: The buttons work, but you can’t see the temperature or settings.
- ✅ Mode Failure: Air only blows from the defrost vents, no matter the setting.
- ✅ Communication Codes: Scanning the vehicle reveals a “U” code for the HVAC Control Head.
Need an Engine or Transmission Computer?
We provide VIN-matched, pre-programmed PCM and TCM units for your vehicle.